Cli doc updates (#681)

* Update usage docs with all subcommands help output.

* Update code block to be standard text.

Author: larrys

crates/weaver_semconv_gen/README.md

@@ -20,7 +20,7 @@ This content will be replaced by generated snippet.
 
 Snippets can be defined with the following pseudo-grammar:
 
-```
+```text
 SNIPPET_TAG = "semconv" GROUP_ID SNIPPET_ARGS?
 GROUP_ID = ('A'-'Z', 'a'-'z', '.', '_', '-')+
 SNIPPET_ARGS = "(" SNIPPET_ARG ("," SNIPPET_ARG)* ")"
@@ -31,7 +31,6 @@ SNIPPET_ARG =
    ("tag" "=" ('A'-'Z','a'-'z','0'-'9')+)
 ```
 
-
 ## Snippet Templates
 
 You can use `weaver_forge` and `minijinja` templates for snippet generation.  When doing so, a template named

docs/specs/multi-registry/multi_registry.md

@@ -133,7 +133,7 @@ The directory structure of a registry remains mostly unchanged, with the additio
 `registry_manifest.yaml`. This file contains the registry metadata, such as the name, version, and description.
 It is required for published registries or registries with dependencies on other registries.
 
-```plaintext
+```text
 registry_root/
   domain_1/
   domain_2/